Some of recent projection type display apparatuses such as projectors that modulate light output from a light source to perform projection, use high-power semiconductor laser elements (LD: Laser Diode) as a light source.
In general, light output from the semiconductor laser element is controlled based on the driving current supplied to the semiconductor laser element. However, once an anomaly such as a malfunction of parts takes place in the driving device for supplying driving current to the semiconductor laser element, an excessive current beyond the rated operation range flows through the semiconductor laser element, hence there is the risk that a high-power density light will be emitted from the semiconductor laser element. Output (projection) of such high-power density light to the outside is not desirable in the above-described, projection type display apparatus using a semiconductor laser element as its light source.
For example, Patent Document 1 (JP2012-084630A) discloses a technology in which a switch provided between a driving device for supplying driving current to an LD and the LD, is controlled to turn on and off based on the current value of the driving current being detected. According to this technology, if the current value of the detected driving current becomes greater than a predetermined threshold, the driving current is determined to be excessive (excessive current), and the switch is turned off to cut off the connection between the driving device and the LD. Since no driving current is supplied to the LD by cutting the connection between the driving device and the LD, it is possible to prevent the LD from emitting high-power density light.